A personal view is presented on progress made during the last 25 years in applying the Three Rs (reduction, refinement, replacement) to animal testing in regulatory toxicology, with an emphasis on "good moments" (for example, international workshops on the principles and practical application of the validation process and on regulatory acceptance) and "not-so-good moments" (for example, the time taken to accept alternatives to the LD50 test and to accept in vitro tests for skin absorption as OECD Test Guidelines). The importance of dialogue and cooperation between international coordinating centres and scientific activities at the national level is stressed, as exemplified by the work of ECVAM during its first decade.